MARS PATHFINDER WINDS DOWN AFTER PHENOMENAL MISSION

After operating on the surface of Mars three times longer
than expected and returning a tremendous amount of new information
about the red planet, NASA's Mars Pathfinder mission is winding down.

Flight operators at NASA's Jet Propulsion Laboratory,
Pasadena, CA, made the announcement today after attempting to
reestablish communications with the spacecraft over the last
month. With depletion of the spacecraft's main battery and no
success in contacting Mars Pathfinder via its main or secondary
transmitters, the flight team cannot command the spacecraft or the
small rover named Sojourner that had been roving about the landing
site and studying rocks.

"We concede that the likelihood of hearing from the
spacecraft again diminishes with each day," said Pathfinder
Project Manager Brian Muirhead. "We will scale back our efforts to
reestablish contact but not give up entirely.

"Given that, and the fact that Pathfinder is the first of
several missions to Mars, we'll say 'see you later' instead of
saying goodbye," he said.

At the time the last telemetry from the spacecraft was
received, Pathfinder's lander had operated nearly three times its
design lifetime of 30 days, and the Sojourner rover operated 12
times its design lifetime of seven days.

"I want to thank the many talented men and women at NASA for
making the mission such a phenomenal success. It embodies the
spirit of NASA, and serves as a model for future missions that are
faster, better, and cheaper. Today, NASA's Pathfinder team should
take a bow, because America is giving them a standing ovation for
a stellar performance," said NASA Administrator Daniel S. Goldin.

Since its landing on July 4, 1997, Mars Pathfinder has
returned 2.6 billion bits of information, including more than
16,000 images from the lander and 550 images from the rover, as
well as more than 15 chemical analyses of rocks and extensive data
on winds and other weather factors. The only remaining objective
was to complete the high-resolution 360-degree image of the
landing site called the "Super Pan," of which 83 percent has
already been received and is being processed. The last successful
data transmission cycle from Pathfinder was completed at 3:23 a.m.
Pacific Daylight Time on Sept. 27, which was Sol 83 of the mission.

"This mission has advanced our knowledge of Mars tremendously
and will surely be a beacon of success for upcoming missions to
the red planet," added Dr. David Baltimore, president of the
California Institute of Technology, which manages JPL for NASA.
"Done quickly and within a very limited budget, Pathfinder sets a
standard for 21st century space exploration."

The Mars Pathfinder team first began having communications
problems with the spacecraft on Saturday, Sept. 27. After three
days of attempting to reestablish contact, they were able to lock
on to a carrier signal from the spacecraft's auxiliary transmitter
on Oct. 1, which meant that the spacecraft was still operational.
They locked on to the same carrier signal again on Oct. 6, but
were not able to acquire data on the condition of the lander. At
that time, the team surmised that the intermittent communications
were most likely related to depletion of the spacecraft's battery
and a drop in the spacecraft's operating temperatures due to the
loss of the battery, which kept the lander functioning at warmer
temperatures.

Over the last month the operations team has been working
through all credible problem scenarios and taking a variety of
actions in attempting to recover the link with Pathfinder. With
all of the most plausible possibilities exhausted, the team plans
to continue sending commands and listening for a spacecraft signal
on a less frequent basis.

"Basically we are shifting to a contingency strategy of
sending commands to the lander only periodically, perhaps once a
week or once per month," said Mission Manager Richard Cook.
"Normal mission operations are over, but there is still a small
chance of reestablishing a link, so we'll keep trying at a very
low level."

Although the true cause of the loss of lander communications
may never be known, recent events are consistent with predictions
made at the beginning of the extended mission in early August,
Muirhead said. When asked about the life expectancy of the lander,
project team members predicted that the first thing that would
fail on the lander would be the battery; this apparently happened
after the last successful transmission September 27.

After that, the lander was expected to begin getting colder
at night and go through much deeper day-night thermal cycles.
Eventually, the cold or the cycling would probably render the
lander inoperable. According to Muirhead, it appears that this
sequence of events has probably taken place. The health and status
of the rover is also unknown, but since initiating its onboard
backup operations plan a month ago, the rover is probably circling
the vicinity of the lander, attempting to communicate with it.

The rover, which went into a contingency mode on Oct. 6, or
Sol 92 of the mission, had completed an alpha proton X-ray
spectrometer study of a rock nicknamed Chimp, to the left of the
Rock Garden, when it was last heard from. The rover team had
planned to send the rover on its longest journey yet -- a 165-foot
(50-meter) clockwise stroll around the lander -- to perform a
series of technology experiments and hazard avoidance exercises
when the communications outage occurred. That excursion was never
initiated once the rover's contingency software began operating.

Now known as the Sagan Memorial Station, the Mars Pathfinder
lander was designed primarily to demonstrate a low-cost way of
delivering a set of science instruments and a free-ranging rover
to the surface of the red planet. Landers and rovers of the future
will share the heritage of spacecraft designs and technologies
first tested in this "pathfinding" mission.

Part of NASA's Discovery program of low-cost planetary
missions, the spacecraft used an innovative method of directly
entering the Martian atmosphere. Assisted by a 36-foot-diameter
(11-meter) parachute, the spacecraft descended to the surface of
Mars on July 4 and landed, using airbags to cushion the impact.
The spacecraft's novel entry was successful.

Scientific highlights of the Mars Pathfinder mission are:

Martian dust includes magnetic, composite particles, with a
mean size of one micron.

Rock chemistry at the landing site may be different from
Martian meteorites found on Earth, and could be of basaltic
andesite composition.

The soil chemistry of Ares Vallis appears to be similar to that
of the Viking 1 and 2 landing sites.

The observed atmospheric clarity is higher than was expected
from Earth-based microwave measurements and Hubble Space Telescope
observations.

Dust is confirmed as the dominant absorber of solar radiation
in Mars' atmosphere, which has important consequences for the
transport of energy in the atmosphere and its circulation.
Frequent "dust devils" were found with an unmistakable
temperature, wind and pressure signature, and morning turbulence;
at least one may have contained dust (on Sol 62), suggesting that
these gusts are a mechanism for mixing dust into the atmosphere.

Evidence of wind abrasion of rocks and dune-shaped deposits was
found, indicating the presence of sand.

Morning atmospheric obscurations are due to clouds, not ground
fog; Viking could not distinguish between these two possibilities.

The weather was similar to the weather encountered by Viking 1;
there were rapid pressure and temperature variations, downslope
winds at night and light winds in general. Temperatures were about
10 degrees warmer than those measured by Viking 1.

Diversity of albedos, or variations in the brightness of the
Martian surface, was similar to other observations, but there was
no evidence for the types of crystalline hematite or pyroxene
absorption features detected in other locations on Mars.

The atmospheric experiment package recorded a temperature
profile different than expected from microwave measurements and
Hubble observations.

Rock size distribution was consistent with a flood-related deposit.

The moment of inertia of Mars was refined to a corresponding
core radius of between 807 miles and 1,242 miles (1,300 and 2,000
kilometers).

The possible identification of rounded pebbles and cobbles on
the ground, and sockets and pebbles in some rocks, suggests
conglomerates that formed in running water, during a warmer past
in which liquid water was stable.

Engineering milestones of the mission included demonstrating
a new way of delivering a spacecraft to the surface of Mars by way
of direct entry into the Martian atmosphere. In addition, Mars
Pathfinder demonstrated for the first time the ability of
engineers to deliver a semi-autonomous roving vehicle capable of
conducting science experiments to the surface of another planet.

The Mars Pathfinder mission is managed by the Jet Propulsion
Laboratory for NASA's Office of Space Science, Washington, DC.
The mission is the second in the Discovery program of fast track,
low-cost spacecraft with highly focused science goals. JPL is
managed by the California Institute of Technology, Pasadena, CA.

JET PROPULSION LABORATORY

Mars Pathfinder Mission Status

October 22, 1997

The Mars Pathfinder operations team is continuing its efforts to
reestablish communications with the Pathfinder lander. Although they are
experiencing communications difficulties, the team is confident that the
spacecraft is still operating on the surface of Mars, according to Mission
Manager Richard Cook. The last time they were able to send a command to the
Pathfinder lander instructing it to transmit a signal back to Earth was on
Sol 93, which was Tuesday, October 7, at 7:21 a.m. Pacific Daylight Time.

Team members suspect that the spacecraft may not be receiving commands
from Earth properly because the lander's hardware has become much colder than
normal. In regular operations, when the lander's transmitter is turned on,
spacecraft hardware warms up sufficiently to operate normally. Since the
transmitter has not been on for several days, engineers suspect that
temperatures within the lander are considerably colder than normal. Predicted
internal temperatures drop to as low as -50 C (-58 F) in the early morning
and only rise to about -30 C (-22 F) in the late afternoon. These temperatures
are about 20 C (38 F) colder than the coldest previous operational
temperatures.

The lower temperatures cause the spacecraft radio hardware to operate
outside the range of radio frequencies that ground controllers have used in
the past. During the past three weeks the operations team has been
transmitting to the spacecraft at a lower frequency and sweeping through a
wider frequency range, a technique that has been used on other missions to
attempt to cause the spacecraft receiver to lock on to the transmitted signal.
Once ground controllers finish this, they send commands instructing the lander
to turn on its transmitter and send a signal back to Earth.

To be certain that they investigate all possibilities, team members are
also consulting with experts knowledgeable about the radio and other key
elements of the spacecraft. They have identified some new scenarios that are
being pursued to regain communications. These recommendations include doing
more testing of the engineering model hardware in the laboratory to better
understand how the spacecraft might be behaving. Another recommendation has
suggested shifting and increasing the range of frequencies being swept through
much more than previously attempted.

According to Project Manager Brian Muirhead, the possibility exists that
an unrecoverable problem may have occurred. Team members expected that, once
the lander's onboard battery died, cold and thermal cycling could result in a
failure of some other element of Pathfinder and thereby end the mission.
"However, the team will continue to do everything possible to reestablish
communications until all options have been exhausted," Muirhead said. The
mission has already exceeded all of its goals in terms of spacecraft lifetime
and data return.

The science team, meanwhile, continues to process and analyze the large
volume of data sent back by Pathfinder's lander and rover. Further science
products are planned and new results will continue to be presented as they
develop.

After 83 days of atmospheric, soil and rock studies, NASA's
Mars Pathfinder lander and rover are continuing extended mission
activities that will take the rover on its longest trek yet and
the lander into new photographic endeavors.

"The lander and rover performance continue to be nothing
short of extraordinary," said Project Manager Brian Muirhead. "We
have proven that we know how to design robust robots to operate
in the hostile environment of Mars."

The rover has just completed its last alpha proton X-ray
spectrometer study for a while, taking measurements of a rock
nicknamed Chimp, located just behind and to the left of the Rock
Garden. Once data from the spectrometer have been retrieved,
Sojourner will begin a 164-foot (50-meter), clockwise stroll
around the lander to perform a series of technology experiments
and hazard avoidance exercises.

Meanwhile, the Pathfinder lander camera is continuing to
image the Martian landscape in full resolution color as part of
its goal to provide a "super panorama" image of the Ares Vallis
landing site. Each frame of this panorama is imaged using 12
color filters plus stereo.

"The super pan will be our biggest and best imaging-data
product," Muirhead said. "It is made up of 1 gigabit (1 billion
bits) of data, of which we've received more than 80 percent.
Given our limited downlink opportunities, we should have the full
image by the end of October."

The 22-pound (10.5-kilogram) rover has survived 10 times
longer than its primary mission design of seven days, while the
lander has now been operating 2.5 times longer than it was
originally expected to operate, according to Richard Cook, Mars
Pathfinder mission manager.

Both vehicles are solar powered, but carried batteries to
conduct nighttime science experiments and keep the lander warm
during the sub-freezing nights on Mars. Normal usage has fully
depleted the rover's non-rechargeable batteries, limiting it to
daylight activities only. The lander battery, which packed more
than 40 amp-hours of energy on landing day, performed perfectly
during the 30-day primary mission, but is now down to less than
30 percent of its original capacity.

"We expected to begin seeing this type of degradation on
both vehicles and, of course, designed both the lander and rover
to operate without batteries altogether," Cook said. "If
everything else continues to operate properly, we could continue
conducting surface experiments for months."

About once every two weeks, the lander battery is used to
perform some nighttime science experiments, he added. The primary
activity is acquiring meteorological data and images of morning
clouds, as well as images of Mars' two small moons, Phobos and
Deimos.

Despite the lack of battery power, the rover has continued
taking successful spectrometer readings during the day. In the
next week, engineers will drive the vehicle back to a magnetic
target on the ramp from which Sojourner first touched Martian
soil.

"This analysis of the dust on the ramp magnet is a very
important science measurement," noted Pathfinder Project
Scientist Dr. Matthew Golombek. "The results should give us a
clue about how all this magnetic dust was formed."

NASA's Mars Pathfinder spacecraft -- a novel mission to send
an inexpensive lander and roving prospector to the surface of Mars
-- has concluded its primary mission, fulfilling all of its
objectives and returning a wealth of new information about the red
planet.

The robotic lander, which continues to explore an ancient
outflow channel in Mars' northern hemisphere, completed its
milestone 30-day mission on Aug. 3, capturing far more data on the
atmosphere, weather and geology of Mars than scientists had
expected. In all, Pathfinder has returned 1.2 gigabits (1.2
billion bits) of data and 9,669 tantalizing pictures of the
Martian landscape to date.

"The data returned by the Sagan Memorial Station and
Sojourner has been nothing short of spectacular, and it will help
provide a scientific basis for future Mars missions, including a
sample return, for years to come," said Dr. Wesley Huntress, NASA
associate administrator for space science. "The Pathfinder team's
"can do" attitude not only was critical to overcoming several
complex technical challenges during development and cruise, but
has carried through the uncharted territory of operating a solar-
powered lander and mobile rover on the surface of a planet
millions of miles from Earth."

A new portrait of the Martian environment has begun to emerge
in the 30 days since Pathfinder and its small, 23-pound rover
began to record weather patterns, atmospheric opacity and the
chemical composition of rocks washed down into the Ares Vallis
flood plain. The rover's alpha proton X-ray spectrometer team,
led by principal investigator Dr. Rudolph Rieder, has been able
to analyze the first-ever in-situ measurements of Mars rocks.

"We are seeing much more differentiation of volcanic
materials than we expected to see," said Dr. Matthew Golombek,
Mars Pathfinder project scientist at JPL. "The high silica
content of one of the rocks we've measured, nicknamed Barnacle
Bill, suggests that there was more crustal activity -- heating and
recycling of materials -- early in Mars' history than we thought."

Similarly, atmospheric-surface interactions, measured by a
meteorology package onboard the lander, are confirming some
conditions observed by the Viking landers 21 years ago, while
raising questions about other aspects of the planet's global
system of transporting volatiles such as water vapor, clouds and
dust, said science team leader Dr. Timothy Schofield. The
meteorology mast on the lander has observed a rapid drop-off in
temperatures just a few feet above the surface, and one detailed
24-hour measurement set revealed temperature flucuations of
30-40 degrees Fahrenheit in a matter of minutes.

In addition, sweeping, color panoramas of the Martian
landscape, created by the Imager for Mars Pathfinder team and
principal investigator Peter Smith, are revealing clear evidence
that the surface of Mars has been altered by winds and flowing
water.

Sojourner, a robust rover capable of semi-autonomous
"behaviors," captured the imagination of the public, which
followed the mission with great interest via the World Wide Web.
Twenty Pathfinder mirror sites, constructed by JPL web engineer
Kirk Goodall and managed by Pathfinder webmaster David Dubov,
recorded 565 million hits worldwide during the period of July 1 --
August 4. The highest volume of hits in one day occurred on July
8, when a record 47 million hits were logged, which is more than
twice the volume of hits received on any one day during the 1996
Olympic Games in Atlanta.

The rover's performance has easily surpassed its designers'
minimum expectations. Engineers designed the roving vehicle's
electronics, battery power and hazard avoidance features to see it
through at least a week of safe roving, not knowing beforehand
what conditions it might encounter on Mars. After 30 days, the
rover is still healthy and has traveled 171 feet in distance,
circumnavigating the lander and taking 384 spectacular views of
rocks and the lander.

"Sojourner's capabilities to detect hazards and then act on
its own to overcome those hazards have been remarkable," said Dr.
Jacob Matijevic, Sojourner project manager. "The technology
experiments we have been able to perform with the rover's wheels
have given us more information about the composition of the
Martian soil, as well as rocks around the landing site.
Sojourner's durability in this frigid, hostile environment also is
showing us that we are on the right track to building smarter,
even more durable rovers for future missions."

Pathfinder's primary objective was to demonstrate a low-cost
way of delivering an instrumented lander and free-ranging rover to
the surface of the red planet. Landers and rovers of the future
will share the heritage of spacecraft designs and technologies
tested in this "pathfinding" mission.

Part of NASA's Discovery program of low-cost planetary
missions with highly focused science goals, the spacecraft used an
innovative method of directly entering the Martian atmosphere.
Assisted by a 36-foot-diameter parachute, the spacecraft descended
to the surface of Mars and landed, using airbags to cushion the impact.

This novel method of diving into the Martian atmosphere
worked like a charm. "Every event during the entry, descent and
landing went almost perfectly," said Richard Cook, Pathfinder
mission manager. "The sequences were executed right on time and
well within our margins."

Pathfinder landed right on the money, within 13 miles of the
targeted landing site. The landing site coordinates in Ares
Vallis were later identified as 19.33 degrees North latitude,
33.55 degrees West longitude.

The spacecraft's terminal velocity as it parachuted to the
ground was higher than expected, said Rob Manning, Pathfinder
flight system chief engineer. "Interestingly, we estimated our
descent on the parachute at about 134 miles per hour. Software
controlling the retro rockets recorded Pathfinder's speed at about
140 miles per hour at the time the rocket-assisted deceleration
rockets fired."

Pathfinder's performance in the Martian atmosphere will be of
great value to Mars Global Surveyor, which will aerobrake through
the Martian atmosphere to circularize its orbit when it reaches
Mars on September 11. The Pathfinder navigation team, led by
Pieter Kallemyn of JPL, estimated that horizontal wind velocities
in the upper atmosphere helped accelerate the spacecraft's descent
velocity by about 20 to 25 miles per hour.

After being suspended from a 65-foot bridle and firing its
retro rockets, a 19-foot diameter cluster of airbags softened
Pathfinder's landing, marking the first time this airbag technique
has been used on another planet. The spacecraft hit the ground at
a speed of about 40 miles per hour and bounced about 16 times
across the landscape for about six-tenths of a mile before coming
to a halt. The airbag seems to have performed perfectly and
sustained little or no damage. To top it off, the spacecraft even
landed on its base petal, consequently allowing its thumb-sized
antenna to communicate the successful landing to a jubilant team
on Earth only three minutes after touchdown.

Science data from the surface of Mars will continue to be
collected and transmitted to Earth, then analyzed by scientists,
as Pathfinder enters its extended mission. The lander was placed
in a two-day hibernation period earlier this week to recharge its
battery after the conclusion of the primary mission, and the
flight team now will begin to power the lander battery off each
Martian night to conserve energy. The rover's batteries remain in
good condition, but are not rechargeable.

The Mars Pathfinder mission is managed by the Jet Propulsion
Laboratory for NASA's Office of Space Science, Washington, DC.
JPL is a division of the California Institute of Technology,
Pasadena, CA.